Suction muffler for a refrigeration compressor

ABSTRACT

A suction muffler for a refrigeration compressor, comprising a hollow body defining at least one dampening chamber that carries a gas inlet duct and a gas outlet duct presenting an inlet opening and an outlet opening, for communicating the interior and the exterior of the dampening chamber, at least one of the gas inlet and gas outlet ducts presenting at least one closed end, one of the inlet and outlet openings being positioned at a certain distance from said closed end, smaller than the distance of said opening in relation to the other opening of the same duct and in a region of the latter presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct and of the cross section of the first of said openings being achieved so as to minimize the gas pulsation noises inside the suction muffler.

FIELD OF THE INVENTION

The present invention refers to a suction muffler for a refrigeration compressor, particularly of the type used in small refrigeration systems, such as refrigerators, freezers, water fountains, refrigerated counters, and which is provided in the region where the refrigerant gas is admitted to the hermetic compressor.

BACKGROUND OF THE INVENTION

As a rule, compressors of the refrigeration systems present, at the suction side thereof, an acoustic dampening system or suction muffler provided inside the shell and which conducts the gas coming from the suction line of said refrigeration systems to a suction valve that is conventionally disposed to provide the selective and automatic opening of a respective suction orifice of a valve plate in which the suction and discharge valves of the compressor are usually mounted.

The suction muffler has, several important functions to the adequate operation of the compressor, such as: to direct the gas, to attenuate the noise resulting from pulsation provoked by suction, to thermally insulate the gas being drawn into the cylinder, and to control the dynamics of the suction valve.

The present refrigeration compressors use the suction muffler of the volume-tube type. This type of suction muffler usually consists of a sequence of volumes interconnected by tubes which conduct the gas coming from the suction line directly to the suction valve. At present, said tubes presenting open ends for the passage of refrigerant gas.

Gas displacement produces pulses, generating noises that are propagated in a direction that is opposite to the gas flow toward the suction valve. The more efficient the suction muffler at its acoustic outlet through which the gas is admitted into the muffler, the lower said pulses.

The influence of the suction muffler on the performance of the compressor is highly important and the dimensioning of both the inner volumes and the length of the tubes of the suction muffler determine, to a great extent, the efficiency of the compressor. While widely used, the known suction mufflers of the volume-tube type have the disadvantage of presenting noise peaks in the specific operational modes of said tubes.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a suction muffler for a reciprocating hermetic compressor, which does not present the inconveniences of the known prior art solutions, producing a better noise attenuation of the pulses resulting from gas being drawn to the suction valve.

It is a more specific object of the present invention to provide a suction muffler as cited above, which allows optimizing the acoustic attenuation for specific frequency bands.

SUMMARY OF THE INVENTION

These and other objects of the present invention are achieved by the provision of a suction muffler for a refrigeration compressor mounted within a shell, said suction muffler comprising a hollow body defining at least one dampening chamber that carries a gas inlet duct having an inlet opening external to the dampening chamber and an outlet opening in the interior of the dampening chamber, and a gas outlet duct presenting an inlet opening in the interior of the dampening chamber and an outlet opening external to said dampening chamber, at least one of the gas inlet and gas outlet ducts presenting at least one closed end, and one of the inlet and outlet openings being positioned at a certain distance from said closed end, along the respective duct, smaller than the distance of said opening in relation to the other opening of the same duct and in a region of the latter presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct and of the cross section of the first of said openings being achieved so as to minimize the gas pulsation noises inside the suction muffler.

The dimensioning of said gas duct and of the cross section of said opening is achieved so as to minimize the gas pulsation noises inside the suction muffler which are generated upon the closing and opening of the suction valve. The region of minimum acoustic pressure is represented as a nodal point of the acoustic mode of the duct.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below based on the appended drawings, given by way of example of one embodiment of the invention and in which:

FIG. 1 illustrates, schematically and partially, a longitudinal sectional view of a compressor carrying a suction muffler;

FIG. 2 illustrates, schematically, a partial cross-sectional upper plan view of a suction muffler constructed according to the present invention, presenting a dampening chamber carrying a gas inlet duct and a gas outlet duct of the suction muffler;

FIG. 3 illustrates, schematically, a longitudinal sectional view of a construction for a suction muffler of the present invention, according to line III-III of FIG. 2, presenting a dampening chamber carrying a gas inlet duct of the suction muffler;

FIG. 4 illustrates, schematically, another longitudinal sectional view of the suction muffler of the present invention, according to line IV-IV of FIG. 2, showing the gas outlet duct of the suction muffler;

FIG. 5 illustrates, schematically, a longitudinal sectional view of another construction for a suction muffler of the present invention, presenting two dampening chambers carrying respective gas inlet and gas outlet ducts of the suction muffler; and

FIG. 6 illustrates, schematically, a graph showing the attenuation curve obtained, for frequency 2 kHz, with a muffler construction of the prior art (full lines) and with the construction of the present invention (broken lines).

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention will be described for a compressor of the type used in refrigeration systems and comprising, inside a hermetic shell 1, a motor-compressor assembly having a cylinder block in which is defined a cylinder 2 lodging, at one end, a piston 3, and having an opposite end closed by a cylinder cover 4 defining, therewithin, a suction chamber (not illustrated) and a discharge chamber 5 in selective fluid communication with a compression chamber 6 defined inside the cylinder 2 between a top portion of the piston 3 and a valve plate 7 provided between the opposite end of the cylinder 2 and the cylinder cover 4, through a suction orifice 7 a and a discharge orifice 7 b, which are respectively closed by suction and discharge valves 8 a, 8 b.

According to the illustrations, the gas drawn by the compressor and coming from a suction line (not illustrated) of the refrigeration system to which the compressor is coupled, reaches the interior of the shell 1 through the suction muffler, generally provided inside said shell 1 and maintained in fluid communication with the interior of the suction chamber of the compressor.

As illustrated in the enclosed drawings, the suction muffler of the present invention comprises a hollow body 10, which is generally made of a material of low thermal conductivity, such as plastic, defining at least one dampening chamber 13, for example internal to said hollow body 10 and carrying a gas inlet duct 20 having an inlet opening 21 external to the dampening chamber 13 and an outlet opening 22 in the interior of the dampening chamber 13 and a gas outlet duct 30 presenting an inlet opening 31 in the interior of the dampening chamber 13 and an outlet opening 32 external to said dampening chamber 13.

According to the present invention, at least one of the gas inlet and gas outlet ducts 20, 30 presents at least one closed end 23, 33, one of the inlet and outlet openings 21, 22, 31, 32 being positioned at a certain distance from the closed end 23, 33, along the respective duct 20, 30, smaller than the distance of said opening in relation to the other opening of the same duct 20, 30 and in a region thereof presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct 20, 30 and of the cross section of the first of said openings 21, 31; 22, 32, being achieved in such a way as to minimize the gas pulsation noises inside the suction muffler.

According to the present invention, each closed end 23, 33, is submitted to the same gas pressure reigning in said region of minimum acoustic pressure.

In the construction illustrated in FIGS. 2 and 3, the suction muffler presents a dampening chamber 13 provided with a gas inlet duct 20 having its inlet opening 21 in fluid communication with the gas supply to the compressor, connected to the suction line of the refrigeration system to which the compressor is coupled and its outlet opening 22 in fluid communication with a suction side of the compressor, for example, directly connected to the suction orifice 7 a of the valve plate 7 of the compressor.

According to a constructive option of the present invention, the outlet opening 32 of the gas outlet duct 30 of a first dampening chamber 13 is maintained in fluid communication with the suction orifice 7 a through another dampening chamber 14, as for example illustrated in FIG. 5, said other dampening chamber 14 having another gas outlet duct 40 having an inlet opening 41 opened to the interior of said other dampening chamber 14 and an outlet opening 42 connected to the suction orifice 7 a.

In the construction illustrated in FIG. 5, the suction muffler comprises a hollow body 10 defining two dampening chamber 13, 14, for example, internal to said hollow body 10 and separated from each other by a common wall 15. To the interior of a first of said dampening chambers 13 projects the outlet opening 22 of the gas inlet duct 20, and an inlet opening 31 of a gas outlet duct 30 has its outlet opening 32 projecting to the interior of the other dampening chamber 14, providing fluid communication between said dampening chambers 13, 14.

In this construction, to the interior of the other dampening chamber 14 also projects the inlet opening 41 of another gas outlet duct 40 having an outlet opening 42 to be connected to the suction orifice 7 a in the valve plate 7.

According to the present invention, each of the gas ducts 20, 30, 40 presents a geometry defined so that at least one of its inlet and outlet openings 21, 22, 31, 32, 41, 42 is positioned at a certain distance from each closed end 23, 33 of the same duct 20, 30, 40, along this duct 20, 30, 40, smaller than the distance of said opening in relation to the other opening of the same duct 20, 30, 40 and in a region thereof presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct 20, 30, 40 and of said cross section of the first of said openings 21, 31; 22, 32; 41, 42, being defined so as to minimize the gas pulsation noises in the interior of the suction muffler, the distance between the medium line of the first of said openings 21, 31; 22, 32; 41, 42 and the closed end 23, 33 of the same duct 20, 30, 40, in which is provided said closed end 23, 33, being greater than half the diameter of said opening 21, 31; 22, 32; 41, 42.

In a constructive option illustrated in FIGS. 2, 3 and 4, the hollow body 10 of the suction muffler presents, internally, only one dampening chamber 13, to the interior of the latter projecting the outlet opening 22 of the gas inlet duct 20 and the inlet opening 31 of the gas outlet duct 30. However, in this construction, the gas inlet duct 20 has a closed end 23 located closer to the inlet opening 21 of said gas inlet duct 20 and defined in a nodal region of minimum acoustic pressure. In this construction, the gas outlet duct 30 may or may not have a closed end. FIG. 4 illustrates a construction in which the gas outlet duct 30, illustrated in FIG. 2, has a closed end 33 provided closer to the inlet opening 31 of said gas outlet duct 30.

According to the present invention, each gas inlet and gas outlet duct 20, 30, 40 may present at least one respective closed end 23, 33 in each dampening chamber 13, 14.

In the construction illustrated in FIG. 5, the gas inlet duct 30 presents a closed end 33 in the interior of the dampening chamber 13, closer to the inlet opening 31 of said gas inlet duct 30. Though not illustrated, it should be understood that the closed end may be also provided adjacent to the outlet opening of the same gas duct.

In another constructive alternative, not illustrated, the opening defined in the region of minimum acoustic pressure is one of the inlet and outlet openings 21, 22, 31, 32, 41, 42 of each gas inlet and gas outlet duct 20, 30, 40 inside the hollow body 10, in a respective dampening chamber 13, 14.

From the definition of the geometry of the gas duct 20, 30, 40 (or other ducts that might be provided in the hollow body 10) provided with at least one closed end 23, 33, an acoustic mode is determined to have a certain attenuated frequency, said attenuation occurring in the region of the gas duct or ducts 20, 30, 40 having a minimum acoustic node, that is, in the regions with minimum pressure. The pressures reigning in each of the gas ducts 20, 30, 40 of the suction muffler are the stationary or acoustic pressures presenting regions of minimum and maximum pressure. Once the minimum pressure regions are determined, one can determine the region to provide said inlet opening 21, 31, 41 or outlet opening 22, 32, 42 and the respective closed ends 23, 33 of each duct 20, 30, 40. Each gas duct 20, 30, 40, provided with an opening or openings in nodal regions, presents each respective closed end 23, 33 constructed in such a way as to avoid any direct communication of the gas with the interior of the hollow body 10 of said suction muffler.

In a constructive option of the present invention, as illustrated in FIG. 3, an inner sidewall portion of the hollow body 10 defines a cover portion in which is tightly fitted the closed end 23, 33 of a gas duct 20, 30, 40, said cover portion being retained therein by appropriate retaining means, such as glue, clamps, projections or by interference. In the constructive options illustrated in FIGS. 4 e 5, each closed end 23, 33 incorporates the respective cover, which is for example defined as a single piece with the remaining of the respective body of the gas duct 20, 30, 40, for example by injection, jointly with the formation of the duct in a single piece, or by over-injection.

In another constructive option of the present invention, the gas duct 20, 30, 40 carries and secures a cover closing an adjacent closed end 23, 33.

According to the present invention, the closed end 23, 33 is defined in a plane intercepted by the direction of the gas flow passing through the opening defined in a nodal region of minimum acoustic pressure of the respective gas duct 20, 30, 40, said opening positioning allowing the pressure to be taken at a point of minimum acoustic pressure, generating high acoustic attenuation in a determined frequency band, as illustrated in FIG. 6.

In another constructive option, the closed end 23, 33 is defined in a plane parallel to the direction of the gas flow passing through the first of said openings 21, 31; 22, 32, 42 of one of the first, second and third gas ducts 20, 30, 40, said opening positioning also allowing the pressure to be taken at a point of minimum acoustic pressure, generating high acoustic attenuation in a determined frequency band, as illustrated in FIG. 6.

Specific aspects of the invention are shown in the figures of the drawings for convenience only, as each aspect can be combined with other aspects according to the invention. Other embodiments will be recognized as possible by those skilled in the art and should be included in the scope of the claims. Accordingly, the description above should be construed as illustrative and not as limitative of the scope of protection of the invention. All such obvious modifications and alterations are found in the scope of protection defined in the appended claims. 

1. A suction muffler for a refrigeration compressor mounted within a shell, said suction muffler comprising a hollow body defining at least one dampening chamber that carries a gas inlet duct having an inlet opening external to the dampening chamber and an outlet opening in the interior of the dampening chamber and a gas outlet duct presenting an inlet opening in the interior of the dampening chamber and an outlet opening external to said dampening chamber, wherein at least one of the gas inlet duct and gas outlet duct presents at least one closed end one of the inlet and outlet openings being positioned at a certain distance from said closed end, along the respective duct, smaller than the distance of said opening in relation to the other opening of the same duct and in a region of the latter presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct and of the cross section of the first of said openings being achieved so as to minimize the gas pulsation noises inside the suction muffler.
 2. The suction muffler, as set forth in claim 1, wherein the gas inlet duct has its inlet opening connected to a suction line of a refrigeration system to which the compressor is coupled.
 3. The suction muffler, as set forth in claim 1, wherein the gas outlet duct has its outlet opening in fluid communication with a suction orifice provided in a valve plate of the compressor.
 4. The suction muffler, as set forth in claim 3, wherein the outlet opening of the gas outlet duct is maintained in fluid communication with the suction orifice through another dampening chamber having another gas outlet duct presenting an inlet opening opened to the interior of said other dampening chamber and an outlet opening connected to the suction orifice.
 5. The suction muffler, as set forth in claim 4, wherein at least one of the gas inlet and gas outlet ducts in the other dampening chamber has at least one closed end, one of the inlet and outlet openings being positioned at a certain distance from said closed end, along the respective duct, smaller than the distance of said opening in relation to the other opening of the same duct and in a region of the latter-presenting a minimum acoustic pressure for a determined frequency, the dimensioning of said duct and of the cross section of the first of said openings being achieved in such a way as to minimize the gas pulsation noises in the interior of the suction muffler.
 6. The suction muffler, as set forth in claim 1, wherein the closed end is submitted to the same gas pressure reigning in said region of minimum acoustic pressure.
 7. The suction muffler, as set forth in claim 6, wherein the distance between the medium line of the first of said openings and the closed end of the gas duct is greater than half the diameter of said opening.
 8. The suction muffler, as set forth in claim 7, wherein the closed end is defined in a plane intercepted by the direction of the gas flow passing through the first of said openings of the gas duct.
 9. The suction muffler, as set forth in claim 8, wherein the closed end is defined in a plane parallel to the direction of the gas flow passing through the first of said openings of the gas duct.
 10. The suction muffler, as set forth in claim 1, wherein at least one closed end is defined by a wall portion of the hollow body.
 11. The suction muffler, as set forth in claim 1, wherein at least one closed end carries a cover.
 12. The suction muffler, as set forth in claim 11, wherein the cover is incorporated to the respective closed end. 